Sign 10 - 75MM Plant Buildings

The 75-millimeter plant, built at a cost of 840,000 dollars, had four factories or production lines. Each line had three buildings connected by a gravity-fed conveyor system and a narrow gauge railroad.

The receiving building accepted one day’s supply of empty shells. The first step was to remove the wooden or metal shipping plug in the nose. Then, the shell was cleaned with a special solution to remove all traces of oil and dirt. Lastly, the shell was painted. Conveyor belts were placed at working height, so the shells were simply rolled off and rolled back on, saving time and the worker’s strength.

In the pouring building, ammonium nitrate was crushed into a fine powder and dried. It was then mixed in large kettles with molten TNT to create the explosive known as amatol. The kettles had hot water jackets heated by a steam coil within the jacket. An agitator assured a well-blended mixture. The total charge of a kettle was about 800 pounds and a new batch could be made every two hours. Because the TNT mixture crystalizes rapidly upon cooling, it was stirred with wooden paddles to break up the large crystals then drawn off into pouring buckets or extruding machines. The charge was poured in small quantities through a funnel placed in the nose of each shell. At regular intervals a special split shell was loaded, taken apart, and examined for defects.

The filled shells were sent to the assembly building where other components like the adapter and primer were added. An important step in finishing a shell was to stencil each bomb so that the gunner would know by its marking how far it would travel once fired on the battlefield.

The chance for explosion was greatest in the pouring building and a lot of thought went into its design. The kettle rooms were separated by thick, brick firewalls which would contain, as much as possible, any explosion. Some of these firewalls remain today.